Re: Emission of cesium 137 -REPLY: Cs volatility/ Industrial Boiler Comparison

["Tony LaMastra" <alamastra@enter.net>]

Stewart - this is in response to your June 27 response to my June 26
posting.   Thanks for your comments.


I do not know what type of steel plant was involved in the Spain incident,
and this will have an impact on the type of furnace(s) and the potential
for emissions to the atmosphere.   Steel is generally made in one of two
ways - either from all recycled feedstocks or a combination of raw
materials plus recycled materials.   If all recycled steel is used, the
steel is typically made in an electric arc furnace in which carbon
electrodes create an arc which melts the scrap - much like what occurs in
electric arc welding.   This is done in a furnace which may hold 10 tons
(very small) to 400 tons (very large).   The majority are around 90 to 200
tons per batch.   The pollution control system attached to this type of
furnace draws the fume (metal oxide dust) into a baghouse under vacuum and
is typically around 90% efficient in collecting the dust.   An induction
furnace is another furnace type that would start with solid steel.  
Induction furnaces are usually always sealed vacuum chambers and are 100%
efficient in collecting emissions.  Induction furnaces are typically used
to produce smaller quantities of high quality steel for very specific
purposes.   

If one starts with raw materials (ores or beneficiated ores such as
taconite), then the iron is reduced in either a blast furnace or some form
of direct reduction furnace.   Blast furnaces are sealed systems and
usually do not release to the environment unless there is a malfunction -
which also means that heat is being lost and the furnace efficiency is
greatly reduced.   The molten pig iron from a blast furnace is then charged
into a steel making furnace, along with scrap steel and the finished steel
is produced.   Generally scrap is not added to a blast furnace, thus it is
highly unlikely a blast furnace melted the source.   Additionally, the
sealed nature of a blast furnace system would make the release very
unlikely.   

Modern steel making furnaces typically have emission collection
efficiencies of also around 90%.   Older technology open hearth furnaces
were typically around 50% efficient.    In both iron making blast furnaces
and steel making furnaces, the bath temperature is around 3000 degrees F,
with some zones exceeding 6000 degrees F.   You are correct that at these
temps, any cesium would be initially disassociated and as the emission
cooled, likely to form an oxide.    However, what we have seen in all the
accidents in the US where cesium 137 has been melted in a steel making
furnace, is that almost all of it has been confined to the dust collected
by the pollution control system (baghouse) and the melt shop, with no
release to the true environment, other than spillage from baghouse conveyor
systems.   This type of release would have been at ambient temperatures
with no likelihood of thermal currents carrying it into the atmosphere.   

There are no "stacks" as is typically seen on a boiler, releasing the dust
into the atmosphere.   This is due to two reasons.   In the case of an
electric arc furnace, the dust has economically significant quantities of
zinc, plus the dust is usually an EPA listed hazardous waste.   For it to
be economically disposed of, the waste is usually treated to remove the
zinc (and receive credit for it) and the hazardous components (lead,
chrome) and the remainder landfilled in a less expensive mode than if it
were still considered a hazardous waste.  In the case of a blast furnace,
the dust is recycled directly back into the blast furnace.   In the case of
a non-electric arc steel making furnace (BOF, open hearth), the dust is
collected for its iron and calcium oxide content and recycled back into the
steel making furnaces.   Thus, it is very difficult for me to imagine how
there would be a large release of material of any form from a steel plant,
unless there was a total breakdown in the furnace and pollution control
systems.   If this did happen, most of the release would settle out on and
around the plant, and present a serious external and internal exposure
hazard - assuming there was enough initial activity to cause detectable
airborne contamination 1000 miles away.   That was the whole point of my
initial posting.   In a system that is designed to not make releases to the
environment, how do we see detectable activity 1000 miles away, and not
hear about catastrophic health effects close to the site? - since it is
highly likely that more was concentrated at the plant than was released
into the environment.

I was surprised to read that home wood ash contains as high as 30,000
pCi/kg.   I was not aware that soil concentrations from fallout exceeded a
few pCi/g (few thousand pCi/kg).    I too have been amazed at the "split
wood, not atoms" bunch, who see nothing wrong with covering a valley in
brown haze from their wood stoves, but object to much more efficient
methods of heat production.


Tony LaMastra
alamstra@enter.net
----------
> From: RADPROJECT@aol.com
> To: Multiple recipients of list <radsafe@romulus.ehs.uiuc.edu>
> Subject: Re: Emission of cesium 137 -REPLY: Cs volatility/ Industrial
Boiler Comparison
> Date: Saturday, June 27, 1998 9:24 AM
> 
> In a message dated 98-06-27 01:50:00 EDT, you write:
> 
> << Also, most steel plants in the more advanced countries have pretty
>  decent pollution control systems.   I have a difficult time imagining
that
>  there was no dust collection system in place.   It is possible that it
was
>  bypassed.   However, if one was in place and operating, it would mean
that
>  there is several thousand pounds of highly contaminated dust - even if
the
>  system was only 50% efficient (modern ones have a much higher collection
>  efficiency).   This would present a serious personnel hazard from both
>  external exposure and potential internal deposition to plant workers. 
>>
> 
> At the high temperatures present in a blast furnace it is likely any
Cs-137
> present would have been going up the stack in gaseous form. Several years
ago
> I  had called for a survey of Cs-137 in woodash after writing a feature
> article in the HPS Newsletter [see Farber, S, "Preliminary Study of
Cs-137
> Uptake by Trees and its implications for BRC, Waste Disposal and
dosimetry",
> Vol. XVIII, No. 4, p. 1-5] I completed a survey of Cs-137 in domestic
> fireplace or woodstove woodash which was presented at the HPS annual
meeting
> in Washington in 1991 [Farber, S and Hodgdon, A, Cs-137 in Woodash
-Results of
> Nationwide Survey". This paper and the nationwide news coverage it
prompted
> ["Wood Ash - the unregulated radwaste?" - Science News] resulted in
several
> studies of Cs-137 in typical large kraft paper mills which burn vast
amounts
> of wood waste and "black liquor" solids. These studies were quietly
performed
> by the paper industry central research division.
> 
> The research at these paper mills showed that greater than 90% of the
Cs-137
> in wood [and in one case about 98%]was volatilized and lost up the stacks
of
> these mills given the very high temperatures in industrial boilers, and
the
> remaining fly ash and bottom ash were quite depleted of Cs. The activity
> balance documented in these studies indicates that each of the 100 large
kraft
> paper mills in the US is releasing more airborne Cs-137 than the average
> nuclear plant. A blast furnace must operate at temperatures even higher
than a
> commercial boiler.
> 
> This low residual Cs-137 in industrial woodash from paper mills stands in
> sharp contrast to the woodash from home burning of wood which showed
Cs-137
> concentrations as high as 30,000 pCi/kg [ 1000 Bq/kg] of ash. The Sr-90
> content of woodash is even higher than Cs-137 in a few measurements I
made.
> This is to be expected because the transfer factors for Sr vs. Cs from
soil to
> wood are quite higher and Sr is quite refractory vs. Cs.  The fascinating
> thing is woodburners --who happen to be quite environmentally conscious
--
> commonly use the woodash from their home fireplaces as a soil amendment
> [because of its potassium content]  in their "organic farming" practices.
It
> is clear that this practice leads to a buildup of Cs-137 in soil. Dose
> calculations bound the dose from Cs-137 after many years of domestic use
as a
> soil additive at about 1 mR per year with the dose from Sr-90 being
perhaps 10
> times higher.  When I posed the tongue in cheek question in my HPS paper:
> "Woodburners and organic farmers -Is it time to kiss your ash goodbye?"
> newspapers and magazines were beating down my door to report on the
issue.
> Organic Gardening magazine, with a monthly paid circulation of just over
> 1,000,000 subscribers, published by Rodale Press, wrote one lengthy
article on
> woodash radioactivity. They reported to their environmentally aware,
generally
> anti-nuclear readers that radiation doses from using woodash in their
gardens
> with elevated levels of  Cs-137 was no big concern since it only resulted
in
> annual doses of a few mR vs. 360 mR/yr WBDE per NCRP-93!! If this point
of
> view were universally adopted by the environmental community it would
have to
> impact some of the dogmatic positions that theoretical doses from nuclear
> waste disposal of  less that 1 mR/yr were some kind of obstacle to
facility
> licensing and operation.
> 
> Stewart Farber, MSPH
> Consulting Scientist
> Public Health Sciences
> 19 Stuart St.
> Pawtucket, RI 02860
> 
> (401) 727-4947  E-mail: radproject@usa.net Fax: (401) 727-2032
> 
> 
>